The present invention relates to tumbler locks and particularly to two stage tumbler locks. The "Abloy" lock, one advanced form of which is shown in U.S. Pat. No. 3,621,689, is a two stage lock now in common usage. Similar locks are shown in the patents to Welch U.S. Pat. No. 2,862,380 and Henriksson U.S. Pat. No. 1,514,318. These various locks have, in common, a housing containing a cylinder which carries a locking member to be moved to and from a locking position. The cylinder is latched to the housing by one or more tumblers. Plural code discs retain the tumblers in latching position. A key is axially inserted into the code discs and is turned to move them to aligned positions. This first stage movement allows the tumblers to unlatch themselves from the cylinder and establish a latching relationship with the discs. Then, second stage movement of the key causes the cylinder to turn, to turn the locking member from its locking to its unlocking position. Relocking is achieved by reverse rotary movement of the key.
A primary object of two stage locks is to make them more secure, i.e., more difficult to pick. The present invention has for its primary object to provide a two stage tumbler lock which is even more difficult to pick than prior two stage locks.
An important feature of the new lock is that instead of having an axially disposed key, it has a peripheral one. This change, coupled with changes in the relationship of the peripheral key to certain other parts, including discs, make the disc bits even more inaccessible than before. Inaccessibility is further enhanced by the provision of a guide or pusher plate to receive the key, and by providing a dog leg in the key so that the inner key portion moves behind the front face of the housing when the key is rotated. Another feature of the new lock is that it has two sets of discs, a first set of actuating discs latched by tumblers to the housing and carrying a locking member, and code discs to hold the tumblers in latching relationship to the housing until the code discs are properly selectively rotated by the peripheral key.
A further feature of the lock is that the key has a camming portion engaging the discs at the time of insertion of the key to bring the discs into desired initial positions prior to rotation of the key.
The subject matter which I regard as my invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, both as to organization and method of operation, together with further advantages and objects thereof, may be best understood by reference to the following drawings, wherein like reference characters refer to like elements.